G.f. A(x) satisfies: A(x) = A(x^2) / (1 - 2*x).

Terms

a(0) =1a(1) =2a(2) =6a(3) =12a(4) =30a(5) =60a(6) =132a(7) =264a(8) =558a(9) =1116a(10) =2292a(11) =4584a(12) =9300a(13) =18600a(14) =37464a(15) =74928a(16) =150414a(17) =300828a(18) =602772a(19) =1205544a(20) =2413380a(21) =4826760a(22) =9658104a(23) =19316208a(24) =38641716a(25) =77283432a(26) =154585464a(27) =309170928a(28) =618379320a(29) =1236758640